Dam Wall Research Articles

A solution for the automatic detection of expansion joints in dam stilling pools using underwater robots

This research addresses the critical challenges of detecting and measuring underwater concrete structure expansion joints (CSEJ), with a particular focus on dam stilling basin environments. A full set of algorithms for detecting expansion joints with underwater robots is presented by the research, enabling real-time and offline analysis along with visualization. These algorithms introduce the use of Convolutional Neural Networks (CNNs) for image feature extraction and segmentation in CSEJ detection, significantly improving accuracy and adaptability over traditional methods. An automated approach known as the Underwater Dam Crack Detection Network (UDCD Network) was introduced by this research. And advanced attention gates and hybrid dilated convolutions to enhance its detection capabilities are incorporated in this system. Additionally, a three-phase deep transfer learning strategy during training was utilized in this research, which significantly improves the model's performance. The research suggests an underwater image restoration algorithm that uses a dark channel prior and dynamic white balance correction to improve image clarity. Furthermore, unique underwater environmental challenges were tackled by this research, such as non-contact measurement of expansion joint widths using a view-geometry-based algorithm and comprehensive detection of dam wall surfaces. Experimental validation demonstrates that the advanced imaging technologies of the proposed underwater robots hold significant potential for autonomous detection of expansion joints in dam stilling basins.

Insights from electrical resistivity tomography on the hydrogeological interaction between sand dams and the weathered basement aquifer

Sand dams, composed of recent alluvial aquifers behind concrete dam walls, are a water management technique in drylands. However, their level of hydraulic connectivity with their surrounding weathered basement aquifer is debated. This study aims to constrain this hydrogeological uncertainty in order to better understand their ability to meet water needs and improve dryland water security. The study is the first to use 2D geophysics (Electrical Resistivity Tomography) to provide evidence of seepage from sand dams at three mature and three newly built sites. A generally greater hydraulic connectivity was found between sand dams and their surrounding aquifer than has been assumed in some previous studies, with sites providing at least some local recharge rather than existing as isolated storage structures. This improved understanding is beneficial for both site selection and the performance of sand dams and can help ensure that maximum benefits are derived from the construction of a sand dam depending on its intended purpose.

The Impact on People who Trade on the Fish Species ‘Limnothrissa miodon’ - Kapenta for their Livelihood: Practical Perceptions of Traders of Siavonga

Lake Kariba is the world’s largest man-made lake and reservoir by volume. It lies 1300km upstream from the Indian Ocean, along the border between Zambia and Zimbabwe. Lake Kariba was filled between 1958 and 1963 following the completion of the Kariba dam at its north eastern end flooding the Kariba Gorge on the Zambezi River. Culturally controversial, the local people believed that the construction of the dam would anger the Zambezi river god Nyami-nyami, who rise up and cause the dam would wall to collapse destroying the bridge as well as resulting in floods of catastrophic proportions. It is believed that the Nyami-nyami lives under a rock close to the Kariba dam wall. The rock is called ‘Kariwa’ meaning trap as the local people believed if you canoed past its location you would be sucked down in whirlpool never to be seen again. This where the name Kariba originates from, laced with the local mythology. In the late 1960s a type of fish Limnothrissa miodon locally known as Kapenta was introduced in Lake Kariba from lake Tanganyika. Kapenta is a small sardine fish which supports a large and viable fishery for Zimbabwe and Zambia. Kapenta, a type of fish also known as fresh water sardine has several chemical compositions that help reduce the risk of various diseases including prostate cancer. A recent chemical composition analysis of Kapenta by the National Food and Nutrition Commission (NFNC) shows a great variation in the nutrient composition for the dry and fresh Kapenta. NFNC principal nutritionist Mr. Musonda Mofu says dry Kapenta contains 209 calories of food energy compared with 85 calories of food energy in fresh Kapenta. In addition dry Kapenta contains 63 grammes of protein and only 16 grams of protein in fresh Kapenta. The paper reflects on the declining population of this small nutrient rich fish due to over-harvesting, climatic changes with increasing temperatures and with the decreasing levels of water storage. A cumulative study on the pattern of nurturing the fish for economic and social flexibility is the main concern of this paper.

A Quantitative Particle-Based Approach for the Geometallurgical Assessment of Tailings Deposits

Tailings generated during ore processing may host significant residual contents of valuable commodities, including critical metals. The particle properties of the tailings, such as mineralogy, particle size, and the surface liberation of ore minerals, strongly control processing behaviour. This study explores a novel combination of methods for incorporating particle data, derived from automated mineralogy, into geometallurgical models of tailings deposits to better understand their reprocessing potential and the economic feasibility of re-mining. This was achieved through binning of different particle types, geostatistical modelling of particle bin frequencies, and bootstrap resampling to reconstruct particle populations. The spatial distributions of processing-relevant particle properties throughout the tailings deposit were predicted with corresponding uncertainties. There are clear systematic trends in the spatial distributions of different particle types, resulting from the sedimentary-style deposition of the tailings. For instance, the tailings nearer the dam walls comprise coarser, silicate-rich particles, while fine-grained and well-liberated sulphide mineral particles are more abundant in the centre of the tailings deposit. As a result, robust models could be developed for the spatial distributions of particle size and mineralogy, which strongly control the sorting of particles during deposition, and other related properties, such as sulphide mineral grain sizes. Finally, a bulk sulphide flotation process was simulated and acid mine drainage potential estimated using the interpolated particle data. Around 58% of the sulphide minerals present could be recoverable by flotation, with the recoverable sulphide portion decreasing towards the centre of the TSF due to the fine-grained nature of the sulphide minerals. The acid mine drainage potential of the tailings is estimated to be moderate to high, indicating that the carbonate minerals present are not sufficient to neutralise the high acid-generating potential of the sulphide minerals. Overall, this study demonstrates how particle-based geometallurgical models can be developed and utilised for practical applications, with the aim of improving the accuracy of resource and reserve estimations of tailings deposits and the sustainable and responsible management of anthropogenic resources. The methodology proposed here can be easily transferred to other tailings deposits.

Methodology for the Identification of Moisture Content in Tailings Dam Walls Based on Electrical Resistivity Tomography Technique

The design of tailings dams has improved significantly in recent decades due to experience and advances in applied research. However, there are still several environmental and geomechanical uncertainties associated with the response of these structures. Failures on the wall of tailings dams are well documented, where the most common causes are related to the action of water overtopping, slope instability, seepage, and foundation failure. Measuring the humidity or the saturation level at tailings dam walls has become a must do in the recent years. Resistivity monitoring using electrical resistivity tomography (ERT) techniques has proven to be one of the tools that provide good subsurface characterization for internal erosion detection and seepage assessment to evaluate potential environmental risks and the physical stability of tailings dams. Also, the integrated techniques of geotechnical, geophysical, and geochemical data have been used to correlate, coordinate, and improve the characterization. In this research, a procedure to guide us to a new methodology of acquiring and monitoring humidity content is presented, in which 2D electrical resistivity tomography (ERT) profiles are linked to the degree of soil saturation, using moisture sensors installed in a nearby well. The ERT profiles provide a 2D resistivity profile, and the moisture sensors can measure resistivity and volumetric water content (VWC) at a given installation depth. This second measure (VWC), with a defined total porosity, can be combined with Archie’s empirical law to obtain the degree of saturation, allowing the possibility to create remote monitoring suitable for mining operations without excessive laboratory testing.

Estimation of the level of anthropogenic impact based on the determination of radionuclides and heavy metals in sediments taken from Rybnik reservoir, Poland

The aim of the study was to estimate the degree of anthropogenic risk by evaluating the level of the contamination of sediments collected from the Rybnik reservoir. The results of the determination of radionuclides (137Cs, 40K, 228Th, 228Ra, 226Ra, 210Pb, 238U) and heavy metals (Zn, Cd, Pb, Cu, Cr, Ni) were presented. The Rybnik reservoir is located in a highly urbanised area, the Lower Silesian Voivodeship in Poland. Radionuclides (137Cs, 40K, 228Th, 228Ra, 226Ra, 210Pb, 238U) were measured using gamma spectrometry. The heavy metal (Zn, Cd, Pb, Cu, Ni and Cr) content was determined using an inductively coupled plasma optical emission spectrophotometer (ICP-OES). The classification of sediment pollution was made on the basis of geochemical and ecotoxicological indices. Radioactivity was varied with the highest for 40K (more than 200 Bq·kg−1). The concentrations for the remaining radionuclides were mostly below 20 Bq·kg−1. At the inlet zone (no. 9) an increase in radioactivity of each radioisotope was observed. The values of heavy metals from the lowest to the highest total amount in the sediments were as follows: Cd < Cr < Pb < Ni < Cu < Zn. The sediments of the reservoir are largely contaminated with Cu, but the sediments generally are contaminated to an average degree. Most pollutants accumulate in the inlet zone and near the dam wall. The content of artificial radionuclides, as well as the geochemical and ecological indicators used, can serve as an indicator of the level of anthropopressure in the vicinity of the Rybnik reservoir.

Zambia–Zimbabwe 2022 hippopotamus (Hippopotamus amphibius) and other species population distribution along Zambezi River

ABSTRACT A hippopotamus and other wildlife species survey were conducted in the Zambezi River between Kariba dam wall and Luangwa River confluence. The main objective of the survey was to establish hippopotamus and other wildlife species population distribution and densities along the Zambezi River. The boat survey method was used on both sides of the river in October 2022 for 262 km. Individual hippopotamus counted were 1769 on the Zambian side and 1424 on the Zimbabwean side. The Zimbabwean side recorded higher hippopotamus pods (138) than the Zambian side (123). Individual hippopotamus density was 26.60/km with a pod density of 0,45/km. There was a significant difference in hippo population between the five Zambezi River sections on the Zambian side ( x 2 = 2345, df = 4, p = 0.01) and Zimbabwean side ( x 2 = 538, df = 4, p = 0.01). The study established areas with high hippo and other wildlife species population distribution and densities, and the study helps to inform management of protected areas’ carrying capacities and management of Human Wildlife Conflicts. The study recommends more studies on hippopotamus migration, population demography, variation in home ranges and regular population surveys in both rivers and inland waterholes.

The hydromorphological effects of dams in an extreme desert environment - The Fish River Canyon, Namibia

Arid ecohydrology relies on sporadic rainfall and flooding to sustain linear river oases, crucial for supporting flora and fauna during the long dry season and drought years. Growing water demands have led to large reservoir constructions, severely impacting the fragile arid ecosystems. We analyse the hydro-geomorphological impacts of the large Neckartal Dam (completed in 2019) on the Fish River oasis based on existing dams, regional studies, field surveys, hydrological data, and modelling. The Neckartal Dam, along with three smaller dams, impounds 80 % of the desert oasis basin (1235 Mm3, 55,870 km2), exceeding the average annual runoff threefold. A gradient of dam-induced changes was identified, varying with distance from the dam wall. Immediate downstream, hydromorphological impacts include channel narrowing (⁓15 %) and reduce mean annual sediment yield (⁓20 %). Also, water distribution losses create chronic low flows, favour for invasive flora and fauna to spread, significantly disrupting the pristine nature of the desert ecosystem. This phenomenon has been observed over a 70 km stretch below the Hardap Dam. This situation is irreversible, as the invasive flora can withstand even large floods. As the distance increases, the dam suppresses low to moderate annual floods and prolongs droughts from months to years or even decades. Based on our flood routing model, only the largest floods (recurrence interval, RI >25 years) can exceed the dam storage, continue downstream, transport sediment and maintain the pool-bar morphology along 245 km of the oasis. The lack of significant flows between major floods means that sediment from smaller, lower arid basins accumulates in the Fish River valley, filling pools and further reducing water availability during dry periods. The Neckartal Dam's impact assessment demonstrates potential changes in arid river systems globally.

Sonlu Farklar Yöntemi Kullanılarak Geçirimsiz Baraj Tabanına Yerleştirilen Palplanş Perdesinin Yerinin Belirlenmesi

In water currents within the ground, a boiling event may occur if the flow direction is opposite to gravity in the outlet area of the flow floor. To prevent a boiling event, the length of the flow path is increased or a weight filter is used in the area where there is a risk of boiling. Increasing the length of the current path is possible by creating an impermeable layer in the upstream (inlet) section of the dam or by making an impermeable sheet pile wall under the dam. The construction of the sheet pile wall under an impervious dam is expensive and difficult. In this study, the sheet pile wall under the dam wall was placed in various positions between upstream region and downstream (outlet) region of the dam, and the value of the dam's seepage rate was analyzed by finite difference method. Vertical seepage rate values and safety numbers against vertical boiling have been found by taking the gradient of the hydraulic head. It has been seen that the sheet pile wall placed in the exit zone of the dam is the solution that minimizes the leakage rate, and, therefore, maximizes the vertical safety number against boiling.

Optimization of Holding Force for a Climbing Robot Based on a Differential Evolutionary Algorithm

Background: The advancements in robotic technology have completely revolutionized day-to-day life. In industrial applications, the implementation of robotics is quite advantageous as it may help in performing dangerous tasks like climbing high walls, working in a high-temperature environment, high radiation exposure conditions etc. Methods: This paper presents the design and development of a wall-climbing robot for dam wall inspection using an adaptive aerodynamic adhesion technique. The optimization of a robot design is done using a differential evolutionary algorithm. Results: In the proposed model, the principle of Bernoulli adhesion is used for designing the suction pad. The optimization of various variables is done using a differential evolutionary algorithm to improve the efficiency and effectiveness of the wall climbing robot adhesion. Conclusion: The results of the proposed system show that the approach can find an optimal holding force and can be effectively used for applications like dam wall climbing for inspection.

Sand dam contributions to year-round water security monitored through telemetered handpump data

Sand dams are a form of rainwater harvesting, prolific in arid and semi-arid lands. Water is provided partly via handpumps, which, as the only improved method of abstraction from sand dams, are important for drinking water security. Accelerometers and cellular transmitters were fitted to 30 handpumps by the Africa Sand Dam Foundation (ASDF) in 2019 to monitor the use and reliability of the handpumps by recording hourly water volume abstracted. Data from April 2019 to October 2021 for 26 of these sites, alongside qualitative data, were analysed and each handpump’s contribution to year-round water security was explored, focusing on the long dry season when water supply from other sources is compromised. ion was over 20 times higher in the long dry season than in any other season, and at sites with higher salinity, higher livestock use, and larger dam wall area. At 21 wells, abstraction was still being recorded at the end of at least one long dry season; however, high spatial and temporal heterogeneity between pumps and seasons means that not all sand dams deliver reliable water supply year-round. Quantifying the contribution that sand dams make to water security is crucial for understanding their resilience against a changing climate and can aid decision makers when choosing the most appropriate water management technique. Knowledge of temporal and site heterogeneity in abstraction can inform when other water sources need increasing and can help with sand dam design optimisation. Overall, our results indicate the positive contribution that sand dams make to year-round water security through the water that is abstracted through handpumps.

Spatial–Temporal Influence of Sand Dams on Chemical and Microbial Properties of Water from Scooping Holes in Degraded Semi-Arid Regions

Communities in semi-arid lands use sand dams to enhance access water during the dry seasons. However, there is limited information on the quality of water derived from these sand dams, especially in degraded lands where storm surface runoff poses contamination risk. Thus, this study aimed at assessing the spatial–temporal variations in water quality of sand dams in Chepareria, West Pokot County in Kenya. Water samples were collected from scooping holes across 18 purposefully selected sand dams. Results obtained showed significant differences in water quality based on a sand dam’s age and location of the scooping holes, but the magnitude of these differences differed with specific properties. For instance, in recently constructed sand dams (&lt;1 year), scooping holes near the sand dam wall had lower pH values (8.5) than holes scooped a distance from the sand dam wall (9.2). For total dissolved solutes and microbial properties, sand dam age had the greatest impact, over the location of the scooping holes. For example, water obtained from &lt;1 year old sand dams had significantly higher TDS with an average value of 100.3 mg L−1. The thermotolerant coliforms (TTC) exceeded the maximum allowable levels recommended by The World Health Organization. Thus, water obtained from these sand dams should be treated before consumption. Finally, sand dams meant for domestic water harvesting should be protected. Shallow wells with appropriate aprons for effective protection against contamination should be installed to enhance abstraction of safe water from sand dams.

Distribution and formation of soil balls under heavy rainstorm conditions in the northern Loess Plateau

The occurrence of a peculiar phenomenon called “soil balls” was observed in Dingbian County, northern Loess Plateau, due to an extremely heavy rainstorm on July 10, 2022. Determining the distribution characteristics and formation of these soil balls is crucial for enriching the knowledge and the precise prevention and control of soil erosion on the Loess Plateau. This research is particularly significant in studying the off-site effects of soil erosion caused by rainstorm and flooding disasters. This study conducted a comprehensive analysis through field investigation and drone aerial photography in the three dam-controlled watersheds selected. The results showed that the soil balls originated from the soil clods generated by landslides and collapses that occurred within the watersheds during heavy rainstorms. Under the action of hyperconcentrated flows, the soil clods were transported downstream. The size of the soil balls is mainly in the range of 20–60 cm in diameter, accounting for 81% of the total soil balls in the dam lands, with significant differences in the morphology at different locations within a dam land region. The average area density and volume density of soil balls in the dam lands of the watersheds are 0.13–0.25 m2 m−2 and 0.05–0.11 m3 m−2, respectively. In each watershed, the area density and volume density of the soil balls exhibit the following order: one-third of the dam land nearest from the dam wall > the middle one-third of the dam land > one-third of the dam land furthest the dam wall. The total erosion intensity of landslides and collapses in the three watersheds was 18,730, 5,213, and 9,879 m3 km−2, respectively. The sediment transport ratio of landslides and collapses expressed by the soil balls in the dam land is at least 4–10%. The study also indicated that the volume of landslides and collapses, the shape coefficient of the watershed, the density of the confluence paths, and the peak discharge had a significant impact on the volume density distribution of the soil balls in the dam lands. We recommend implementing certain measures in similar watersheds, including converting steep slopes into terraced fields or grasslands, constructing water storage and drainage facilities, building energy dissipation measures in channels, and reinforcing check dams, to reduce the risk of soil ball events occurring under heavy rainstorm conditions, and protect the ecological environment on the Loess Plateau.

Longitudinal recovery gradient of macroinvertebrates during different hydrological scenarios in a downstream river reach

Macroinvertebrate community composition in regulated rivers is highly dependent on high and low flow events. Significant reduction or augmentation of the flow downstream from a dam can lead to a decrease in the variety of the sensitive macrozoobenthic taxa. Such decreases may lead to a degraded ecological status. In this research, the macrozoobenthic community was investigated in a river section downstream of a multipurpose dam with strategic significance for northeast Bulgaria. Samples were collected for five years from the Golyama Kamchia River, in close proximity to the Ticha dam. Three sampling sites were established in a longitudinal gradient, from 75 to 1770 meters from the dam. Sixteen invertebrate samples were taken between 2017 and 2021. Double sampling (spring and autumn) was conducted in 2019. The goal was to find how macroinvertebrate communities are influenced by the dam-induced modified environmental conditions, from the management of the dam, and which of the parameters is considered to have the strongest effect. Likewise for the study was important to understand longitudinal recovery gradients from the application of the present “minimum acceptable flow – compensation flow” in hydrologically differing years. The main physicochemical parameters were measured alongside the velocity of the water at each sampling site. Additionally, the maintained hydrological regime was explored for a relationship by several hydrological indices with the macroinvertebrate community composition. The analysis of the biological data through 7 biological indices showed that hydrologically sensitive taxa (Ephemeroptera, Plecoptera and Trichoptera - EPT) were very good indicators for damming impact, detecting disturbances not so well differentiated by other type-specific indices and the resulting ecological status. The order Trichoptera was the most influenced taxa group during the study. In 2020 the base flow released from the dam dropped to its lowest level (0.095 m3 s-1 from 0.552 m3 s-1) for an explored 10-year period of hydrology. This event continued for more than a year and led to a rupture of the previously observed recovery gradient. Downstream of the second sampling site, at about 800 m below the dam wall, a decrease in the number of trichopteran families was observed and at the third site, at 1.8 km from the dam they were significantly reduced.

Water quality characteristics of Vanderkloof Dam and its potential for rainbow trout farming

Vanderkloof Dam was periodically sampled between November 2014 and April 2016 for a range of water quality parameters to assess the potential for cage culture of rainbow trout, Oncorhyncus mykiss. The dam is strongly stratified in summer and autumn, although upper water column temperatures remain relatively cool, largely &lt;25°C. The dam is considered oligotrophic, characterised by phosphorus limitation of primary production, particularly during summer. Light is strongly attenuated in the epilimnion and heterotrophic community metabolism is observed through much of the water column. Surface nutrients are depleted through the summer with phytoplankton assemblages dominated by the green algae, Oocystis lacustris, Desmodesmus bicaudatus and Coelastrum microporum. The water column turns over during the winter and the nearly isothermal impoundment approaches 11°C. Nutrients are re-introduced into surface waters following winter mixing coincident with an increase in diatoms. The preferred environmental window for rainbow trout becomes severely contracted during the summer in that epilimnion temperatures exceed 21°C and thermocline/hypolimnion oxygen concentrations fall below 3 mg‧L−1. The coincidence of relatively high pH &gt;9.5 could exacerbate these physiological challenges. Hydrological conditions for fish farming are most suitable in the proximity of the dam wall as opposed to further upstream. Here the hypoxic conditions that develop in the thermocline/hypolimnion during summer and autumn are less pronounced, particularly towards the southern bank, where concentrations of total suspended solids are generally &lt;10 mg‧L−1 and water clarity is more favourable for visual feeders such as fish. Although rainbow trout may survive the adverse conditions prevalent during the summer, growth is likely to be compromised and susceptibility to disease may increase.

Boundary element model for the analysis of the dynamic response of the Soria arch dam and experimental validation from ambient vibration tests

This paper presents a 3D boundary element time–harmonic model for the analysis of the dynamic behavior, under low-level vibrations, of the Soria arch dam (Gran Canaria, Spain). The model takes into account dynamic Soil–Structure Interaction (DSSI), Fluid–Structure Interaction (FSI) and the actual geometry of dam wall and reservoir. The rock and the dam wall are considered as viscoelastic regions, and the water in the reservoir is modeled as an inviscid fluid. The influence of DSSI, FSI, height of the water in the reservoir, accuracy of the geometric modeling of the canyon, and type of transmitting boundary conditions at the truncated end of the reservoir, are evaluated. DSSI and FSI have a significant influence on the dynamic response of the dam, and the accurate representation of the geometry of the canyon is relevant for the correct estimation of the modal shapes. Ambient vibrations tests were also performed, from which the first and third modes could be clearly identified. The comparison between the experimental and numerical natural frequencies and mode shapes suggests that the proposed complete numerical model is able to capture the dynamic response and can be used for the structural health monitoring of the wall of this dam.

Controlling blooms of Planktothrix rubescens by optimized metalimnetic water withdrawal: a modelling study on adaptive reservoir operation

BackgroundAggregations of cyanobacteria in lakes and reservoirs are commonly associated with surface blooms, but may also occur in the metalimnion as subsurface or deep chlorophyll maxima. Metalimnetic cyanobacteria blooms are of great concern when potentially toxic species, such as Planktothrix rubescens, are involved. Metalimnetic blooms of P. rubescens have apparently increased in frequency and severity in recent years, so there is a strong need to identify reservoir management options to control it. We hypothesized that P. rubescens blooms in reservoirs can be suppressed using selective withdrawal to maximize its export from the reservoir. We also expect that altering the light climate can affect the dynamics of this species. We tested our hypothesis in Rappbode Reservoir (the largest drinking water reservoir in Germany) by establishing a series of withdrawal and light scenarios based on a calibrated water quality model (CE-QUAL-W2).ResultsThe novel withdrawal strategy, in which water is withdrawn from a certain depth below the surface within the metalimnion instead of at a fixed elevation relative to the dam wall, significantly reduced P. rubescens biomass in the reservoir. According to the simulation results, we defined an optimal withdrawal volume to control P. rubescens blooms in the reservoir as approximately 10 million m3 (10% of the reservoir volume) during its bloom phase. The results also illustrated that P. rubescens growth can be most effectively suppressed if the metalimnetic withdrawal is applied in the early stage of its rapid growth, i.e., before the bloom occurs. In addition, our study showed that P. rubescens biomass gradually decreased with increasing light extinction and nearly disappeared when the extinction coefficient exceeded 0.55 m−1.ConclusionsOur study indicates the rise in P. rubescens biomass can be effectively offset by selective withdrawal as well as by reducing light intensity beneath the water surface. Considering the widespread occurrence of P. rubescens in stratified lakes and reservoirs worldwide, we believe the results will be helpful for scientists and managers working on other water bodies to minimize the negative impacts of this harmful cyanobacteria. Our model may serve as a transferable tool to explore local dynamics in other standing waters.

Discrete Particle Method Numerical Simulation on The Distributions of Suspended Particles in The Flow of Ogee Spillway Structure

Dam failure is undeniably catastrophic and one of its major causes is the soil erosion near the dam structure. In this paper, the characteristics and compositions of soil sediment in dam spillway structure were investigated to determine its impact on the occurrence of erosion. Four suspended samples were taken from the vicinity of Ogee dam spillway. Sediment analysis using scanning electron microscope revealed that the soils consist of relative high metal contents of aluminium, iron and magnesium. These metals will attribute to the erosion of dam wall, which subsequently reduce the durability of wall against high hydrostatic pressure exerted by the reservoir. Nonetheless, as the average sizing of suspended particles at each sampling location were capped at 4.55 μm, the damages incurred to the dam were minimal. Additionally, the suspended particles around the dam spillway was numerically simulated with the inclusion of discrete phase model. The numerical data were in great consensus with the corresponding finding attained from the particle image velocimetry experimental of a scaled-down dam model, with the discrepancy not more than 4.89 %. The movement of suspended particles due to the water flow can be tracked numerically and it is found the sediment prone to accumulate at the vicinity of dam spillway.

Evaluation of water quality and dam for sustaining the fish population dynamics

Bhagirathi is a Himalayan River, which flows in Uttrakashi district in Uttarakhand state. It is one of the most important streams of the Ganga River. This river is famous for dam construction and fisheries development. The fishes of commercial importance in cold water are Mahaseer, Snow Trout. The fish production depends on the physical, chemical as well as biological qualities of water. In the present paper, water quality evaluation and dam in the sustaining fish population dynamics have been reviewed to make aware the fish culturist and environmentalist about the water quality factors which influence health of a pond and to increase the fish yields to meet the growing demands of present time scenario of the our country. The construction of dams causes many problems. Water quality and discharge of water from the dam wall systems also indirectly affect the fish populations. In this study, we also review some of the important impacts associated with dams and their recommended mitigation measures. There is a negative impact on fish population dynamics, especially for downstream habits due to dams. Water quality is measured like temperature, turbidity, carbon dioxide, pH, alkalinity, hardness, BOD, TDS, Turbidity. The maximum oxygen content of water was recorded in January 13.02 ± 0.166 mg l−1 and minimum 9.4 ± 0.05 mg l−1 in July in site I phase I (before the reservoir dam wall). While in site II and phase I (After the dam), the maximum DO was observed in the month of January of 12.1 mg l−1 and minimum in July of 8.93 mg l−1. This is because water level is minimized in site II almost dried in winter. The CO2 of the Maneri Bhali phase I -Site I (before dam) was recorded maximum in April 3.10 ± 0.012 mg l−1. In Maneri Bhali phase I -Site II (After dam), the CO2 was recorded maximum 3.01 ± 0.003 mg l−1 in the month July. The river of Garhwal Himalaya harbors a rich aquatic diversity, the most common endemic fish species that inhabit this fresh water is the Schizothorax species. The maximum no. of fish were observed in winter and minimum in monsoon. At present, the production of these fishes from the streams is very poor and is not well managed from recreational and conservation point of view. If such is developed properly, it can have revenue potential for our state government. Sports, fisheries, tourism should be promoted.

Tailings dams: Assessing the long-term erosional stability of valley fill designs

Tailings is a generic term for waste material from the extraction and processing of minerals and frequently contain mineral and chemical residues. They are usually highly erodible and transportable via fluvial processes. Tailings are commonly stored in ‘tailings dams’ and such dams are a feature of many mine sites. As they impound water and sediment, tailings dams can be at risk from both catastrophic and gradual failure, especially if unmanaged. A fundamental question for their management is, can tailings dams ever be walk-away structures? Catastrophic failure occurs when there is a large scale rapid structural failure of the dam wall suddenly releasing large volumes of water and sediment. However, over time, there will the increased risk of gradual failure by the slow infilling of the dam and the erosion of the dam wall. Failure can occur where water overtops the dam wall and then incises through the wall due to a loss of freeboard in the dam, a situation which is more likely in legacy tailings dams where they have been filled, vegetated and abandoned. Here, firstly, a computer based landscape evolution model (CAESAR-Lisflood) is employed to assess a hypothetical tailings dam failure by erosion. Secondly, using an idealised example, it is demonstrated that given average climate conditions a dam can be sufficiently robust to last centuries. Thirdly, and longer term it is demonstrated that the tailings can be contained if (a) maintenance is conducted to increase the dam wall height over time or (b) a more robust dam wall is constructed to manage extreme events. However, erosion and infill will continue to reduce the integrity of any structure over time. Therefore, it is highly likely that tailings dams will require continued monitoring and maintenance. The method outlined provides a new tool for assessing any tailings facility for its erosional stability.